Well prior to receiving the Nene, the Soviets were working off copied German jet engines. They found themselves unable to perfect the technology thus necessitating the advent of the Nene. Without it, the Soviets are left with little other choice than to continue down the road they were on. Fortunately for them, this isn't a dead end, the French managed to do something similiar with their Atar engines and they turned out all right.
What it probably does mean is that the MiG-15 as we know it is probably butterflied away. Without the reliable powerplant of the Rolls Royce Nene, I doubt the Soviets are going to attempt a single engine design. In all likelihood the ungainly MiG-9 will probably be further refined, given bigger engines, swept wings, redesigned control features etc. while the Soviets work on perfecting their copied German engines like the French did in OTL.
Come the Korean War TTL's MiG 15 (more like a MiG-9) doesn't sweep the floor with the UN fighters and is roughly equal to the P-80. However this does little more than delay the advent of the F-86.
Eventually I suspect the Soviets will come up with a workable design and proceed to develop better fighters but not in time for the Korean War...